Kaesong Industrial Zone, an area located in the Cold War-era DMZ between the two Koreas, has earned an estimated $2 billion a year in trade for the impoverished North Korean state. The joint factory zone remained closed to South Koreans for a second day on April 4, 2013, after North’s government shuttered access amid a spiraling diplomatic crisis. Factories in the Kaesong Industrial Park are still believed to be operating, but North Korea’s decision to block entry is a further sign of the growing tensions on the Korean peninsula.